min, max, base
Set logarithmic contour levels for mapplot.

EXAMPLE
-------

0>loglevs 0.5
The new contour levels are:
 -0.5 0.5 1 2 4 8 16 32 64
0>

The second and third lines are output lines from loglevs and show the
resulting levels assigned to the levs variable.

PARAMETERS
----------
min  -  The lowest (positive) level to include. The levels list starts
        with  -min,min,... ie. The first positive level is also used as
        the only negative value.

max  -  (Optional: Default=100)
        This is the highest (positive) level to include in the levels
        listing. Thus:  loglevs 0.5,2  produces  -0.5,0.5,1,2 .

base -  (Optional: Default=2)
        The scale factor between subsequent levels in the listing.
        Thus:  loglevs 0.5,2,1.5  produces  -0.5 0.5 0.75 1.125 1.6875 .

CONTEXT
-------
The full dynamic range of a contour plot is often most cleanly
represented by an exponentially increasing set of contour levels
(conventionally called logarithmic levels).

The contour levels used by subsequent calls to the mapplot command
are defined in a user-variable called  levs. One way to set these
levels is to directly assign them:

For example:

0> cmul=0
0> levs=-1,1,2,4,8,16,32,64

Defines a set of percentage contour levels starting at -1% and
increasing exponentially up to 64%.

It is tedious to have to type out the levels explicitly in this
way. The loglevs command provides a more convenient means to
assigning "logarithmic" levels to the levs variable. Thus the
above example could be achieved by typing:

0> cmul=0
0> loglevs -1

RELATED COMMANDS
----------------
mapplot  -  Display map and beam images.
xyrange  -  Set the boundaries of the sub-image to be displayed in mapplot.
loglevs  -  Set logarithmic levels.
mapcolor -  Select mapplot colormap type and transfer function.
mapfunc  -  Change the transfer function used in mapplot.
beamloc  -  Change when and where mapplot plots the clean beam ellipse.